Frequency of bilateral temporomandibular joint disc displacement in patients with unilateral symptoms: a 5-year follow-up of the asymptomatic joint. A clinical and arthrotomographic study.

Bilateral arthrotomography was performed in 50 consecutive patients with unilateral symptoms of disc displacement to evaluate the frequency of temporomandibular joint disc displacement in asymptomatic joints. Using well-defined clinical criteria, there were no false-positive findings of either reducing or non-reducing discs. On the other hand, a risk of false-negative diagnosis of non-reducing disc was apparent. Sixty per cent of the patients had a non-reducing displaced disc in the asymptomatic joint. Most of these patients could recall a previous spell of discomfort from this joint. Severe or moderate deformation had taken place in non-reducing discs, while reducing discs were normal in shape or had, at most, a thickening of the posterior band. The duration of symptoms was significantly correlated with the degree of deformation in the symptomatic joints (P less than 0.01). Perforation was statistically, significantly correlated with disc deformation and, in symptomatic joints, hard tissue changes. Fifty-seven per cent of the asymptomatic joints with displaced discs developed pain following the onset of symptoms from the contralateral side, most within 2 years. Less than half of them were free of pain at the end of the 5 year follow-up period. In view of this tendency for an asymptomatic joint with a displaced disc to subsequently develop pain refractory to treatment, such a joint must be considered a weakened link in the craniomandibular system, vulnerable to changes in mandibular function such as, for instance, displacement of the disc on the contralateral side.